Accelerator



Patented Dec. 3, 1940 UNITED- STATES PATENT OFFICE aooamaa'roa Rex P. Cosgrove, Toledo, Ohio, assignor to Plaskon Company, Incorporated, Toledo, Ohio, a corporation of Delaware No Drawing. Application August 6, 1938, Serial No. 223,524

2 Claims. (Cl. 260-71) The invention relates to a novel carbon compound, which is a latent accelerator for formaldehyde-urea molding compositions.-

. When a thermosetting molding composition, 5 such as a formaldehyde-urea composition, is molded under elevated pressure and temperature, it first softens and then hardens at the molding temperature, whereas a thermoplastic composition remains soft until 'the molded article has i cooled. As a result, an article molded from .a

thermosetting composition can be removed from the mold after a relatively shorttime and while I much molding equipment for the same volume ofproduc'tlon, and hot-molding equipment is ex- 25 pensive.

Formaldehyde-urea molding compositions are thermosetting, but articles molded therefrom must be left in the heated mold for a short time after the article has become hard enough to be so removed, in order that a resin of optimum properties may be produced. It has been found that curing the resin by keeping it at the molding temperature for the proper length of time is required to bring out its optimum properties.

35 There is of course a demand for formaldehydeurea moldingcompositions for which a-relatively short period of curing is necessary.

\ A latent accelerator in aformaldehyde-urea molding composition is an ingredient that ac- 40 celerates the curing of the composition without materially impairing its stability in storage at ordinary temperatures. True latent accelerators are very rare. They may be alkaline, neutral,

or so slightly acid that they .do not appreciably 45 acidifypa molding composition when added thereto.;' It is believed that they are substances that break up or undergo molecular rearrangement to ,form acids, but do not do so until the molding temperature is reached. The acids so formed 6 must \be strong enough to serve as catalysts that hasten the" curing of the formaldehyde-urea resin. Formaldehyde-urea molding compositions contain appreciable moisture, and are frequently Ii kept in storage for weeks at a time before being used. Many substances that might be expected to decompose to form acids under molding conditions suifer the same decomposition within a few hours after being intimately mixed: with a formaldehyde-urea composition, and are therefore not latent accelerators. Moreover, the behavior of a substance when present as a minor ingredient in a molding composition and subjected to molding pressures at the molding temperatures of 130 to 160 C. cannot be predicted 10 from its behavior when subjected by itself to temperatures of 130 to 160 C. at atmospheric I pressure. Most of the potentially acid substances. that do not. impair the stability of a molding composition when incorporated therewith likewise do not accelerate the curing of the composition in the mold.

A substance that materially impairs the sta-- bility of a molding composition is a highly undesirable ingredient. The manufacturer of a 201 formaldehyde-urea molding composition must. mold articles forvarious periods of time at various temperatures and pressures and carefully test them to determine the molding conditions and curing time required to give the desired resuits. If a molding composition contains an ingredient that materially impairs the stability of the composition, articles molded from the composition will be inferior, not only because the composition gradually deteriorates during storso age, but also because the molding conditions required for producing articles with the,desired properties from batches of the composition that have been stored for'various periods under various conditions are indeterminate.

Although certain halogenated organic compounds that liberate hydrobromic and hydro chloric acid when heated have been known to act as latent accelerators when incorporated in formaldehyde-urea molding compositions, accelo ,erators that liberate organic acids are preferable to accelerators that liberate strong inorganic acids. Certain organic peroxides, such as benzoyl peroxide, have been used heretofore as latent accelerators, but there are many organicpigments that cannot be used in a molding composition containing a peroxide. 7

The principal object of the invention is to provide a novel latent accelerator for formaldehydeurea molding compositions. More specific ob- 6 iects and advantages are apparent from the description, which merely discloses and illustrates the invention and is not intended to impose limitations upon the claims;

The novel latent acceieratgr of the present in- El A formaldehyde-urea'molding composition of the usual type, consisting primarily of celluloslc ma erial (40 to and a formaldehyde-urea re tion product, may be employed.

Example The starting materials for the preparation of the present latent accelerator are benzoyl chloride and lacthydroxamic acid OH OH 0 on when... are.)

A solution of lacthydroxamic acid may be prepared as follows: Hydroxylamine hydrochloride (35.2 grams) is suspended in 200 c. c. of methanol, and warmed. Sodium hydroxide (20.4 grams) is then suspended in another 200 c. c. of methanol, heated to boiling, and added to the other methanol suspension. All the sodium hydroxide then'goes into solution, and the liquid is cooled. The precipitate which forms isdiltered oil, together with a small amount of undissol'ved hydroxylamine hydrochloride, and ethyl lactate (60.8 grams) is added to the clear solution. The solution is then allowedto stand until half of the methanol has evaporated (about 20 hours), and the liquid is then filtered to remove the further precipitate that forms.

The novel latent accelerator may be prepared from the resulting solution by adding a concentrated solution of 19.15 grams of potassium hydroxide in water, and then adding 48 grams of benzoyl chloride gradually in small portions. The accelerator precipitates, and maybe filtered off, dissolved in methanol, and reprecipitated from the methanol by the addition of water. Its melting point is 155 C. One part of this substance may be ground in a ball mill, together with parts of alpha-cellulose fiber impregnated with 200- parts of a formaldehyde-urea reaction product. The customary modifiers, such as lubricants, plasticizers and coloring matter may also be added to the ball mill. After an intimate mixture has been obtained in the form of a fine powder, it may be granulated or formed into pellets so that it can be used conveniently for charging molds. The molding of the composition is performed under a suitable pressure at a temperature of about C. k

Various other applications of the invention may be devised to meet/various requirements.

Having described my invention, I claim:

1, A composition comprising a thermosetting formaldehyde-urea reaction product and a latent accelerator which has a melting point of about C. when pure and which is substantially identical with the substance obtained by treating lacthydroxamic acid with benzoyl chloride.

2. A composition comprising a thermosetting formaldehyde-urea reaction product, cellulosic material, andjrom about 3 to about /2 per cent of a. latent accelerator which has a melting point of about 155 C. when pure and which is substantially identical'with" the substance obtained'by treating lacthydroxamie acid with benzoyl chloride.

REX P. COSGROVE. 

